The carbs and flowmeters really don't matter much as to which range of
flow to design/select for. What counts is the displacement of the
engine, the RPM of interest, and the volumetric efficiency (into which
parameter I will toss effects of less-than-wide-open throttle.)
use (displacement * RPM/2) * volumetric efficiency = volume flow rate
For round numbers, most non-race-prepared engines will have a maximum
volumetric efficiency at wide-open throttle and torque-peak RPM of
about 80%. If you want to flow substantially more than that (say at
power-peak RPM) just use the larger RPM and don't worry about the
volumetric efficiency too much.
e.g. (1296 cc * 6000RPM/2) * 0.80 = 3110400 cc/min or 3110 litres/min
which is the same as (79.1 CI * 6000/2) * 0.80 = 189840 in3/min
or 110 cfm
If you are concerned about tests at idle or small part-throttle
conditions, it would be fairly safe to assume that air flow rate is
proportional to horsepower, so a road-load power requirement of 20 HP
in the example engine (with the ability to produce 80 HP max) would
probably use about or a little more than 27.5 CFM or 780 litres/min.
Donald.
> From: "Ken Gano" <triumphs@mcleodusa.net>
> Date: Sat, 5 Feb 2000 09:04:03 -0600
>
>
> I have seen a tool listed in the Pierce Manifold catalog that purports to
> measure the airflow through Weber carbs. I am thinking that I can make a
> similar tool as I have access to industrial flow meters. Does anyone know
> range of flow these meters measure? I am using it on DCOE 45 on a TR3. Are
> they calibrated in cubic feet per minute or liters per minute or something
> else?
>
> Any help is greatly appreciated.
>
> Ken Gano
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